A feasibility study or the time l'Volution of a long-lived vu bea!ll '~ performed. The proton momentum (1.5 GeV/c) was chosen to concentrate tlia vu flux at ver~ low energy where all background re~ctions are kirematically suppres sed. Sensitiv i ty to oscillations at lar ge proper times 1 • t/p (wlwre t is the [light lcugth and p is the momentum of the neutrino) is gre~tl y enh~n c ed by the r e sulting low neutrino momentum, Possible tra~sformations v + v (searched for via v n + e-p reaction~)

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... were not ob s! rved in a n e~Posur~ of 2xlOl8 protons oR targec. Ten possible vun • u p cve1ts \Je re observed, 1\n upp e r limit of 3eV, comparable to previous limits, ca11 be pla c e d o tt tit~ 1nas s diffe~cn c e b~tweeo the two nelltrinn et~enstates. The ac celeratcr ba ckRrounds are lo~ and the neutrino fluxes copious so that an ~x p e r ime nt to approach a ma s s differ ence limit of 'SleV i.s currently po:>.:; i hl c . FuLu f C' CKp (·r im C' nt s '"lth lonr.,c r d is t ;mcc s ~nd ];"lrg~r nm.E S£' 5 could t't.•: ••:h 0 . 1\• V ;tt tl w 1\t:S , ,."tllparahll• l n tlt4..• ht.•:->t .llmil~ propi'l!'>l'r ;uul t' '-' ; 1\.: lll l" t.'X pl.!r i uh.! l\t n . Presented hy ~-Sulak ut Lhe 1\GS Fi xed Target Work shop Nuvvmb c r H-9, 1 97ft *Supported in part by the United States Department of Er_ergy. 233 Proposa 1 s to search for neutrino evo 1 uti on at llrookha ven were submitted in January of 1977. Since then the many problems associated with extracting and transmitting an intense, high repetition rate, low energy proton beam ·were so 1 ved in severa 1 short pre 1 iminary tests. An extended run of two weeks duration allowed beam optimization and coiMlissioning and evaluation of a new target and focusing horn. The last t~10 days of this run had beam conditions sufficiently clean and stable to take physi~s data. We first discuss the physics motivation and possible current and future experiments. We then sulllnarize the principal accomplishments of the tes t periods. r-------NOTICE-------,